Vaping and smoking is banned on hospital sites. It’s the method not the prescription the staff seem concerned about? From reading other people experiences hospitals do accept the use of cannabis being vaped in certain circumstances, some hospitals even offer a separate isolated room to vape. However it’s unreasonable to think every hospital be able to provide this and the reality is the NHS is already stretched enough.
As a cannabis patient prejudice unfortunately this is not uncommon but I really do believe that this is a lack of awareness and understanding.
I don’t think the security guard was that bothered he was just doing his job, he is just following the instructions he has been given by the hospital staff and that seems to be to asked you to not smoke or vape in the hospital entrance.
Maybe writing a letter to the hospital to explain why you feel that your rights where not recognised and what provisions are in place for yourself and others patients in regards to using medical cannabis products on site.